When I've been talking about chores with the kids I have been categorizing it as something you choose to do because you love your house, love your family and love helping others (See Family Motto). It's a simple explanation and I think they get it. They have had chores in their rooms for a while...keep floor clear of toys and clothes, keep closet organized, put away clean clothes into drawers, etc.
I've been making a big deal about the PRIDE that comes from a clean space with signs and praise. I have found that what works best for us is to set the timer for 15 min every day when we get home (Fly Lady) and we all three clean up our rooms...at the end I go on and on about how proud I am of my clean room and they do the same and then I say "Now that we have our rooms clean and our chores done we can have some FUN!"